As a method for preparing malonic acid monoesters, chemical hydrolysis of malonic acid diesters is commonly used. According to this method, however, it is difficult to separate the generated malonic acid monoester from the unreacted malonic acid diester and the malonic acid which is a by-product. Thus, it is impossible to obtain highly pure malonic acid monoesters.
As a method for obtaining highly pure malonic acid monoesters, a method using Meldrum's acid as a raw material is known [see, for example, Matoba Katsuhide et al., Chem. Pharm. Bull., 31 (8), 2955 (1983); or Rigo B. et al., Tetrahedron Lett., 30(23), 3073 (1989)]. However, since this method uses expensive Meldrum's acid, it cannot be said a practical method and is not suitable for industrial production.
As another method for obtaining highly pure malonic acid monoesters, a method is known in which malonic acid diesters are treated with an enzyme or microorganism having an ability to hydrolyze ester bonds (Japanese Unexamined Patent Publication No. 8-173174). However, the use of malonic acid diesters as a raw material is disadvantageous in terms of cost.
Therefore, development of a highly productive method for preparing highly pure malonic acid monoesters has been desired.